Thanks for your responses to my comments about "first operational use of radar"
and the relative vulnerability of Bismarck and Hood to lucky hits. Here's some additional explanation and/or clarification of my comments in light of your responses.

Dave Saxton - Operational Use Of Radar

Dave notes:

It was not the first operational use of radar.
. . . . . . . . . . . . .
It was the first use of Type-284 by the British. The British had used radar a few months previously in the Med against the Italians. In that case it was Type 279.

Actually it was the first operational use for shadowing, according to Rear Admirral Wake Walker's After Action Report:

10. This was, I fancy, the first occasion that R.D.F. has been used for shadowing and the supreme value of it for this purpose cannot be over emphasised. Suffolk made good use of it but I think the long ranges she obtained during the day must have made her a little over-confident during the night when she must have been near the limit of the R.D.F. range. This left no margin to cover a sudden change of course of the enemy such as was likely during the dark hours. Unless it brings the shadower within effective gun range of her quarry, it is considered that at night touch should be kept within 25 per cent of the ascertained R.D.F. range in hand.

Captain Ellis of Suffolk calls its use to shadow at night experimental:

29. 0306 (B). Re-established Type 284 contact. No change. Zig-zagged 30° out for ten minutes, and back, during which time Type 284 contact was lost.

30. 0326 (B) - 0401 (B). Searching towards enemy's last bearing, until it became certain he had either turned round to starboard and worked eastwards under the stern of the shadowers, or he had altered course south-westward to draw ahead and away. This took rather long to conclude, partly because of the onset of fatigue (Suffolk have been steaming at considerable speed either in pilotage waters or following the enemy for four consecutive nights), and partly because night R.D/F tactics were still only experimental.

These first hand accounts were good enough for me to conclude that Tovey and Holland would not hang their hat on this unknown. Plus as you pointed out, they had a good idea ahead of time that its effective range was only 25,000 yards. The key to my alternate plan was that the risk of losing contact would be much less if Hood and PoW added their radars to Suffolk's. A 25% safety margin would be close enough for Bismarck to visually identify them and then use her known speed advantage to outrun the effective gun range of their radar.

As to German Radar:

The Germans had been using it operationally from day 1, and had operational radar that was quite capable and surprisenly sophisticated from 1938.
. . . . . . . . . . . . . .
The German Seetakt radar in 1941 could track capital ships to 30km.

Here's what Wake-Walker said about it.

9. I was always wondering if the enemy were using R.D.F. to locate us, but I have the feeling that his R.D.F. is linked with his gun control and does not search independently. Otherwise the cruiser should have been prepared for us at 2030 on 23rd and on various other occasions when clearing visibility brought us in sight at ranges from 8 to 13 miles. That he does fire at unseen targets is shown by the experience of the aircraft and destroyers when actually fired at under those conditions.

I was exaggerating to be funny, which you appreciate, given your wink about my BMW comment. Here's a more sober analysis.

Your general view is that before Denmark Straits Holland didn't have enough information about Bismarck to assess her vulnerability to being crippled or sunk by one lucky hit, so he had to assume it was about the same as his ships.
In addition and setting aside assumption in favor of facts, she wasn't so toughly built to give her some special exemption from a lucky hit. lwd points out that after Denmark Straits the ship received the worst pounding ever by big naval guns and the hull was still afloat, as evidence that she wasn't vulnerable to such a lucky hit.

Both points illustrate something Holland didn't know at the time he would have while weighed whether to engage or shadow, and how lack of knowledge favors engaging. They differ on how tough Holland's target actually was, but I think they can be reconciled when you realize Holland's real issue - whether Bismarck's ability to sustain battle damage without being sunk or operationally crippled, compared to that of his ships, was so superior that the odds are affected? He would be thinking about how resistant she is to decisive battle damage; sinking her with a lucky hit is one of the ways to do that, but he needs hits that damage or destroy essential functions that her mission or getting home require.

Basically, you have to separate the hull and deck citadel from the upper works, vulnerability of each essential function from its reliability, and sinking by gunfire from decisive battle damage by gunfire.

1) The compartmented hull, its armor and the deck armor make sinking an order of magnitude more difficult that any other ship, as well as decisive battle damage to the power plant and magazine functions in the citadel (it's almost immune to gunfire and requires torpedos to sink).

2) The hull and deck do not protect functions in the hull outside the citadel (fuel storage, steering, propellers and shafts) from decisive battle damage any better than any other ship. One lucky hit or more likely several hits can impair or destroy these functions and make the ship unable to do its mission or get home.

3) The upper works do not protect its functions (navigation, command, weapons, direction, detection, communications) from decisive battle damage any better than any other ship. If I recall correctly, certain defects (location of wires?) made some of these upper work functions more vulnerable than those of other ships to impairment or destruction by one lucky hit. Other functions like the guns require a number of hits, but one or more could make the ship unable to do its mission or get home.

4) As to 1, 2 and 3 above, I also think that generally the mechanics of the ship were not rugged enough for the high seas. The Germans didn't have much experience with these demands on machines because historically they thought of the Baltic, North Sea, coast protection and short voyages. Their other ships seem to have spent a lot of time in repairs and Bismarck may have been the same. The ship was more vulnerable to a breakdown that could have the same consequences as decisive battle damage.

5) 2, 3 and 4 are magnified by the fact that the ship would essentially be alone on the high seas. It is one ship against the whole British Navy and Air Force assisted by the U.S. She is surrounded by hostile shores so no friendly port is available, while the enemy has many. The French and Norwegian ports were subject to air attack so it has to go around Britain for real safety in Germany.
These factors magnify the consequences of any decisive battle damage in terms of the rest of the voyage - the damage is permanent and makes it easier for the enemy to force battle again and on better terms. They also diminish the ship's greatest advantage because although it is difficult to sink it is easier to damage the ship enough to make it useless.

It was indeed the first time that the British had used radar for shadowing, but the Germans had used radar for that purpose many times by 1941. WW is just guessing about the effectiveness of Seetakt in tactical roles and he guessed wrongly. The Seetakt antenna was mounted on the rotating rangefinder hoods because it provided a fully stablized mounting and 360* scanning, plus it could be used to range targets for gunlaying. Seetakt was a multirole radar system. The Seetakt radar had been used effectively to detect and avoid unwanted enccounters with enemy warships, blind navigation, finding shipping commerce to attack, stalking merchant shipping at night, shadowing convoys at night or in bad weather, finding tankers and supply ships in fog, and numerous other general tactical uses, since the beginning of the war. The Scheer had detected a patrolling cruiser while passing through the Denmark St a few months previously, so it ducked into a fog bank and watched the British cruiser steam on by on its radar. Now that the British had more effective radar, patrolling cruisers could detect the German ships in situations were they would not have been aware of the Germans being there previously. The Germans were certainly tracking WW's cruisers with radar even if he didn't think so.

The precise knowlege of the relative locations, course and speeds, and the behavior of the British shadowing ships after dark were obviously being supplied by Luetjens' radar and it allowed him to formulate a more effective plan to break contact.

WW did guess correctly that the German radar was well suited to naval gunlaying roles, and that it had already been used successfully many times to help target DD's and aircraft, as well as large warships.

Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

I agree with tnamel ... although I can't spell his "name", with one exception.

I haven't seen any evidence that Bismarck had reliability problems or that she wasn't a good sea boat. She was new, so her equipment was all in excellent condition. I've never seen anything to indicate she or her sister had gunnery problems due to turret flooding in the Atlantic, unlike S&G. She was much larger, so that wouldn't be too surprising.

tnemelckram wrote:...lwd points out that after Denmark Straits the ship received the worst pounding ever by big naval guns and the hull was still afloat, as evidence that she wasn't vulnerable to such a lucky hit.
....

I'm not sure I did. For instance I think Yamashiro may well have taken an even worse pounding. Furthermore POW hit, Rodney's hit that apparently took out half her main battery, and the torpedo hit on her rudder could be considered luck hits that had considerable impact on her ability to complete her mission. The close range punding Bismark endured later in her final engagment was also one unlikly to produce "lucky" hits that were going to result in a catastropic sinking. The use of cased ammo also meant that even if a round found her magazines a catastrophic explosion was not a foregone conclusion.

As I recall if the projectile must travell through much sea water the likelyhood of such a hit penetrating to a vital space intact was very remote. The sea water scrubbs off almost all of the energy of the shell, and it causes the shell's trajectory to become very unpredictable. Additionally, often the shell is yawed sideways.

I studied how much sea water a shell would have to travell through to get under the belt of the Bismarck and it is a minimum of 6 meters with an angle of fall of exceeding 30-35*. At lower trajectories the distance it would need to travel becomes enormous. The historical hit occured at compartment XIV, and in that case there was probably a wave trough created in that area due to the wave forms created by the extremely high speed the Bismarck was steaming at the time. Even then the shell only retained enough energy to get to the wing tanks and not past the longitudinal armoured bulkhead.

Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

...and the similar hit on Prince of Wales probably occurred because the fuze delay element failed to burn through resulting in a dud shell which had just sufficient energy to dent the torpedo bulkhead before falling into the bilges. Had the fuze operated properly, the .035-sec pyrotechnic delay would have burst the shell short of the ship. However, that said, Murphy's law has not as yet been repealed, and there will always be the element of extraordinary circumstances to permit that which should not logically be possible.

Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.

Dave Saxton wrote:.... Additionally, often the shell is yawed sideways....

My understanding is that the shells are actually more stable underwater moving base first so if they travel any significant destance they tend to flip over and assume that configuration. Obviously they are sideways for the transition. On one of the boards (perhaps the IJN board) I've seen a number of drawings depicting the under water trajectories observed in actual test. This was in relation to the Japanese "diving shells" which were optimised to try and take advantage of just this sort of hit. The current thoughts seam to be it wasn't worth it.

Fiven the entrance variability (swells mean that angle of entrance can vary widely even at a fixed range) it's certainly not very predictable. At Bismarks last battle I think others here have mentioned that when the British vessels closed the shells that hit short were skipping rather than diving. At longer ranges the shells will tend to go deep pretty fast. It would seam there is a somewhat limited regime where there is any likelyhood of such hits even occuring.

Yes projectiles with relatively pointed noses, such as FMJ spitzer-type bullets, uncapped base fuzed shells, and the like will frequently turn in water and stabilize themselves base first. Shells with very blunt piercing caps, assuming the ballistic cap has been shed, may or may not do the same. The 38cm shell which hit Prince of Wales below the waterline may or may not have followed a base first trajectory in the water, as the ring and knob type cap should have given a good stable underwater trajectory. That said, the shell might have tumbled going into a trough or through a wave crest. Round nose projectiles and those with flat noses generally do better--hence one tends to find torpedoes with relatively blunt noses as opposed to streamlined ones--early attempts at streamlined torpedoes led to instability and poor accuracy.

The Japanese attempt to design a specialized diving shell with a detachable upper piercing cap and very long fuze delays may well have been an exercise in futility and probably degraded the shell performance against normal strikes against armour or allowed it to go completely through a lightly armoured target before detonation could occur.

Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.